*3.1. Theoretical Basis for Overall Optimization of the PLES*

The goal of PLES optimization is to achieve a "win–win" PLE situation, which is the key to ecological civilization construction [39]. Achieving a win–win PLE situation is the basic principle of environmental management put forward by Ye [40], based on China's basic situation. The core idea of this principle is that environmental governance should not involve disruptive, passive, or excessive governance, or damage the economy. Tian Daqing et al. argued that a win–win PLE situation should not only be the goal criterion of sustainable development, but also the behavioral judgment criterion of sustainable development. Based on this concept, Gao [41] constructed an evaluation system for comprehensive management of the water environment in small watersheds, and endowed this system with the scientific connotation of a win–win PLE situation.

The optimization of PLES should be based on the carrying capacity of resources and the environment, and be carried out in accordance with the principle of balance between the population, resources, and the environment, in order to coordinate the development of the land-use structure and scale of PLES [7]. Scientific evaluation of the carrying capacity of resources and the environment, and the suitability of territorial space development, are key to scientifically develop a PLES [42]. Therefore, in order to achieve the goal of a

win–win PLE situation, the overall optimization of PLES should be supported by regional sustainable development theory, human–Earth system coupling theory, system science theory, spatial equilibrium theory, and community theory.

#### 3.1.1. Theory of Sustainable Development

The theory of sustainable development refers to development that meets the needs of the present without jeopardizing the ability of future generations to also meet their own needs. Sustainable development includes common development, coordinated development, fair development, efficient development, and multidimensional development; the core theories of sustainable development are the theory of sustainable utilization of resources, externality theory, and three production theories [43,44]. In PLES, the intensive and efficient production space emphasizes improving the intensive utilization level and output efficiency of production space, that is, the economic goal; appropriate living space refers to improving the quality of life and livable level of residents, that is, the environmental goal; the beautiful ecological space attaches importance to improving the ecological service function and the quality of ecological environment, that is, the environmental goal; the overall planning of PLES is the optimization goal of coordinating different functional spaces to maximize the comprehensive benefits of the economy, society, and environment. Therefore, the overall planning and optimization of PLES is an important practical way for the goal of a "beautiful China" and China's SDGs. To meet the strategic needs of territorial space optimization, the coordinated optimization and overall development of PLES should be guided by the sustainable development concept of "people-oriented" development to develop scientific cognitive methods, and clarify the basic logic problems relevant to the situation.
